Noise suppressors for jet engines



1958 J. M. TYLER ETAL 2,845,775

NOISE suPPREssoRs FOR JET mamas Filed June 1, 1956 3 Sheets-Sheet 1 mew-INVENTORS JOHN M- TYLER I 20 ROBERT E- MEYER //0 0| lG 9A ATTORNEY 1958J. M. TYLER ETAL 2,845,775

NOISE SUPPRESSORS FOR JET ENGINES Filed June 1, 1956 3 Sheets-Sheet 2INVENTORS JOHN M- TYLER ROBERT E- MEYER ym iMM ATTORNEY Aug. 5, 1958 YJ. M. TYLER ETAL 2,

NOISE SUPPRESSORS FOR JET ENGINES I5 Sheets-Sheet 3 Filed June 1, 1956'Y/wnm ATTORNEY 2,845,775 Patented Aug. 5, 1958 NOISE surrnnssons son JETENGINES John M. Tyler and Robert E. Meyer, Glastonbury, Conn.,

assignors to United Aircraft Corporation, East Hartford, Conn., acorporation of Delaware Application June 1, 1056, Serial No. 583,742

17 Claims. (Cl. hu -35.6)

This invention relates to the suppression of low frequency, audiblenoise and more particularly to the suppression of low frequency, audiblenoise from the exhaust of any type of a jet and in particular anaircraft jet engine wake.

Since a modern jet aircraft engine produces noise energy ofapproximately 200 horse power and since such noise would interfere withconversations at a distance of as much as 3000 feet from the engine, itis obvious that steps must be taken to control the formation of noisefrom the jet engine. The novel method of accomplishing this noisecontrol taught herein is to shift the noise created to a predominatelyhigh frequency spectrum so that it will not interfere with airportpersonnel and the populace in the vicinity of airports.

The theory of noise creation and suppression utilized in our inventionis described more fully in U. S. patent application Serial No. 581,418to which reference may be had.

It should be borne in mind that in our invention we are not reducing theintensity of noise which has already formed but, we are controlling thecreation of noise by passing the jet exhaust gas through a plurality ofsmall nozzles instead of through a single large nozzle. The resultaccomplished is to have noise created in a predominately high frequencyspectrum as opposed to a low frequency spectrum. Low frequency spectrumsprovide objectionable noise while a high frequency spectrum providesnoise which is of a lesser audible intensity. Our invention lies in theapparatus for accomplishing this spectrum change.

It is an object of this invention to prevent the creation of audiblenoise, or control the creation of audible noise during the groundoperation of aircraft jet engines and other jets and also during flightoperation of aircraft jet engines.

It is a further object of this invention to control the creation ofnoise from an aircraft jet engine wake by causing the exhaust gases ofthe engine to be discharged through a plurality of small nozzles in thetrailing edges of hollow radial extending vanes, which vanes may beretracted to form the engine tailcone.

it is a further object of this invention to provide a noise suppressionapparatus which will not interfere with the thrust created by anaircraft jet engine both in flight and during ground operation, whichwill not unduly increase the engine diameter, in fact, which will notincrease the engine diameter at all in certain embodiments, which willnot require sealing or valving, which will not create drag and which isso constructed that a smaller exhaust gas outlet is presented by theengine parts, not including the noise suppressor parts, during normaloperation as opposed to operation with the noise suppression apparatusfunctioning.

While we choose to show our invention with respect to the control of thecreation of noise by an aircraft turbojet engine, such is done forpurposes of illustration only, and it should be borne in mind that theprinciples disclosed herein are applicable to noise creation control onany type of aerodynamic exhaust. In the drawing:

Fig. 1 shows a cross sectional view of a typical turbo-jet engine withan embodiment of our invention attached thereto and shown in itsretracted position in solid lines while shown in its operative positionin phantom.

Fig. 2 is a fragmentary cross sectional view of an embodiment of ourinvention with the noise suppressor vanes retracted.

Fig. 2A is a fragmentary cross sectional view 'of an embodiment of ourinvention with the noise suppressor vanes in their operable position,

Fig. 3 is a partial rear view of the embodiment shown in Fig. 2.

Fig. 3A is a partial rear view of the embodiment shown in Fig. 2A.

Fig. 4 is a view taken along line 4-4 of Fig. 2A.

Fig. 5 is a fragmentary cross sectional view of another embodiment ofour invention which shows the noise suppressor vanes in their retractedposition.

Fig. 5A is a fragmentary cross sectional view of another embodiment ofour invention which shows the noise suppressor vanes in their operableposition.

Fig. 6 is a partial rear view of the embodiment shown in Fig. 5.

Fig. 6A is a partial rear view of the embodiment shown in Fig. 5A.

Fig. 7 is a perspective view of adjacent noise suppressor vanes of thetype used in Figs. 5, 5A and 6.

Fig. 8 is a fragmentary cross sectional view of the embodiment of ourinvention shown in Fig. 11 showing the externally clustered vanes intheir operable position.

Fig. 8A is a fragmentary cross sectional view of the embodiment of ourinvention shown in Fig. 11 showing the externally clustered vanes intheir retracted position.

Fig. 9 is a fragmentary cross sectional view of the embodiment of ourinvention shown in Fig. 11 showing the internally clustered vanes intheir operable position.

Fig. 9A is a fragmentary cross sectional view of the embodiment of ourinvention shown in Fig. 11 showing the internally clustered vanes intheir retracted position.

Fig. 10 is a view thru line 10-10 of Fig. 8A, enlarged.

Fig. 11 is a rear view of another embodiment of our invention whichconsists of both a plurality of internally clustered vanes and aplurality of externally clustered vanes.

Fig. 12 is a perspective view of the externally mounted vane shown inFigs. 8, 8A and 11.

Referring to Fig. 1 we see aircraft jet engine 10 which consists of airinlet 12, compressor section 14, combustion chamber section 16, turbinesection 18, and exhaust outlet section or tailpipe 20. It will be notedthat Fig. 1 shows a plurality of hollow, fin-type vanes 22 which have asingle hole 24 in the forward edge of each vane and a plurality of smallholes or nozzles 26 in the trailing edge of each vane. Vanes 22 areshown clustered in their inoperative position (solid lines) to form theengine tailcone in combination with movable inner body 28. Vanes 22 arealso shown in their operable or silencing position in phantom. Withvanes 22 in their operating position, inner body 28 has moved forward asshown in Fig. 2A in this embodiment.

Air enters engine 10 through air inlet 12 and is compressed as it passesthrough compressor section 14. The air is then heated as it passesthrough combustion chamber section 16 due to the combustion which takesplace within combustion chamber 30. Fuel enters combustion chamber 30through fuel manifold 32 and fuel nozzles 34. Spark plug 36 causes theignition of the atomized fuel from fuel nozzle 34 within combustionchamber 30. As theheated air leaves combustion chamber section 16 itpasses through turbine 18 and then is discharged through the gas passagewhich is formed between tailpipe 20 and inner body 28. When vanes 22 arein their retracted position, so as to be clustered downstream of innerbody 28 to form a conical continuation thereof the exhaust gas passesthrough exhaust outlet 33, which exhaust outlet'SSis formed by tailpipe20-and inner body 28, which is concentric with tailpipe 20 and containedtherein. The exhaust gases are permitted to pass through exhaust outlet38 when noise suppressionis notdesired. As mentioned supra and morefully described in U. S. application Serial No. 58,418 entitled, GroundExhaust Noise Suppressors, and filed April 30, 1956, the discharge ofthe exhaust gases through the large nozzle or exhaust outlet 38 createsa low frequency noise. When noise suppression is desired, vanes 22 arepivoted radially outward into their extended position so as to extendthrough or across the gas passage formed by tailpipe 20 and inner body28 and extend radially outward of tailpipe 20. Relatively large hole oraperture 24 in the forward edge of vane 22 intercepts or is presented tothe .gas passage and causes the exhaust gases to pass through hollowvane or fin 22 and be discharged through the .plurality of relativelysmall holes, nozzles or apertures 26 in the trailing edge of vane 22. Asmentioned supra and more fully described in referenced application, thiscauses the noise created by the jet wake to fall into a predominatelyhigh frequency noise spectrum.

Figs. 2, 2A, 3 and 3A show one embodiment of our invention of a jetengine exhaust noise suppressor.mechanism in greater detail.

It should be-noted that Figs. 2 and 3 demonstrate'the suppressionmechanism in its retracted or non-silencing position while Figs. 2A and3A show the noise suppression mechanism in its operable position. Whenthe vanes 22 are in their retracted position (as in Figs. 2 and 3),axially movableinner body 28 has moved rearwardly on rollers 40 whichpivot in inner body at 41 andbear against support member 43 so as toform a smooth tail- .cone with the plurality of retracted vanes 22 whichare clustered to form a cone just downstream of inner body 28.

It will be noted that hole 24 in the forward edge of vane 22 is notblocking off when vane 22 is retracted 'as it is not deemed necessarysince there is no significant pressure drop across the inlet hole 24 andthe outletholes 26 of vane 22.

With vanes .22 in their retracted position, exhaust gas flow is throughthe gas passage formed between tailpipe 20 and inner body 28 such thatthe exhaust gas passes through exhaust outlet 38. It will be noted thattailcone 20 has inwardly directed scallops, trough or dimples-42 whichbutt against or come into close proximity to inner body 28 in severalplaces about the inner periphery of tailpipe 20 as best shown in Fig. 3.The function performed by theplurality of progressively inwardlydirected troughs 42 is to block off the exhaust gas passage betweenadjacent hollow vanes 22 when they are in their extended position, asshown in Figs. 2A and 3A. If this area were not blocking oft, theoptimum effect of passing the exhaust gas through nozzles 26 would notbe realized since the pie shaped segments formed between adjacent hollowvanes 22 when extended, would present large nozzle areas from whichexhaust flow and low frequency noise would be created. It is necessary,to avoid drag, that troughs 42 be smoothly faired forwardly or upstreamso that it gradually and smoothly blends into tailpipe 20 at theirforward end. While inwardly directed troughs 42 may be integral withtailpipes 20 as by being formed from the same piece of sheet metal astailpipe 20, it is also possible that they may be separate piecesafiixed to tailpipe 20.

Referring to Fig. 3 we see thatiduring normal flight operation, whichwill be a non-silencing operation, the engine exhaust'gas passes througha plurality of-openings "fluids.

Fixed member 50 includes hydraulic cylindrical wall 38 which are formedbetween inner body 28 and tail'conc 20 and are bounded by adjacentinwardly directed troughs 42. In this configuration, due to theexistence of inwardly directed troughs 42 a symmetrical but interruptedand non continuous exhaust outlet is presented. This is contrary to theusual concept of an exhaust outlet which presents a continuous exhaustarea which is formed between two concentric members of circular crosssection.

Now referring to Figs. 2A and 3A, we see hollow noise suppressor vane 22in its extended or operable position. With vanes 22 in this position theexhaust gas flow passesbetween tailpipe 20 and inner body 28, which isnow in a position forward or upstream of what it was when the vanes wereretracted, and then enters hole 24 in the forward edge of vane 22 andmay be turned substantially radially outward by turning vanes 44 andafter passing through hollow vane 22 to be discharged rearwardly intoatmosphere through the plurality of rearwardly directed nozzle 26 on thetrailing edge of vane 22. As best shown in the lower half of Fig.3 sincethe inwardly directed troughs 42 block off the area'between vanes 22,all of the exhaust gas must pass through vanes 22 and then through smallareaholes or nozzles26. By

use of the apparatus just described, the result of discharging theexhaust gases through a plurality of small nozzles as opposed to onenozzle is accomplished, thereby causing the noise created by thedischarged exhaustgas to be predominately in a high frequency, inaudiblespectrum instead of a predominately low frequency spectrum. It isimportant that the thrust generated by engine '10 in normal flight beunaffected by the silencing operation.

.For this reason, the number and size of vanes 22 and nozzles 26 are soselected that the tested fiow characteristics of the gas flow throughexhaust outlet 38 is the same as through nozzles or holes 26.

Now referring to Figs. 2 and 2A relativeto the mechanism which is usedto actuate the plurality of hollow vanes 22 to either rotate radiallyinward or .cluster into conical form and form the engine tailcone incombination with inner body 28 and also to rotate radially outcontactsupport cylinder 43, .as shown in Fig. 4.

Fixed member 48, which may be cylindrical in shape, is'provided,together with fixed member 50, which is also cylindrical in shape andconcentrically located infixed member '48, to form passages forpressurized actuating Seal 51 is provided to seal fluid in member St).

member or piston 52 at its rearward end. If it is desired to cause theplurality of hollow vanes 22 to assume their operative, silencing orradially extended position as shown in Figs. 2A and 3A, a source ofcompressed fluid, probably compressed air from compressor section 14 ofeninner body 28, the leftward movement of cylinder 53 causesthe-leftward or forward movement of inner body 28 such that the innerbody is moved to the far left or forwarded position shown in Fig. 2A andthe plurality of vanes 22,-which pivot both about fixed pivot point 68and movablepivot points -62 and 64. Movable pivot 'point"64-=joins vane-22-to inner-body 28 such that the forward or upstream movement of innerbody 28 causes vane 22 to pivot or rotate radially outward to assume theposition shown in Figs. 2A and 3A. It will be noted, that with vanes 22in this extended position and with inner body 28 in its upstream orforward position, the gas passage formed between inner body 28 andtailpipe 22 is of greater radial dimension R0, than the radial dimensionRr of the gas passage when the plurality of noise suppressor vanes areretracted radially inward to cluster and form the engine tailcone withinner body 28. To cause vanes 22 to retract uniformly, compressor airsource is no longer directed into hydraulic compartment 54. but is nowdirected through fixed member 50 into hydraulic compartment 66 so as tocause a rearwardly directed force against face 68 of hydraulic cylinder53 to cause hydraulic cylinder 58 and inner body to move to the right,rearward or downstream to assume the position shown in Figs. 2 and 3.The movement of inner body 28 caused by the movement of hydrauliccylinder 53 and the pivot action which occurs at pivots 6t), 62 and d4,previously described, causes hollow supprcssor vanes 22 to rotateradially inward and rearwardly to cluster into conical form as shown inFigs. 2 and .3.

It will be noted that this embodiment has accomlished noise suppressionwithout the need for valving or sealing flaps.

Figs. 5, 5A, 6, 6A and 7 show another embodiment of our invention inwhich the hollow vane noise suppressors are shown in their retractedpositions in Figs. 5 and 6 and in their extended or silencing positionsin Figs. 5A and 6A. In the non-silencing or vane retracted position theexhaust gas flow is between tailpipe 2G and inner body 23, which isfixed and terminates short of said tailpipe 2t). It will be noted thatthe plurality of hollow noise suppression vanes 22 cluster in conicalformation downstream of inner body 28' so as to form the engine tailconeand to act in unison with tailpipe 2% to provide a continuous exhaustgas outlet 33 between vanes 22 and outlet 79 of tailpipe It will benoted that due to the particular shape of hollow noise suppressor vanes22', a relatively small and probably supersonic exhaust outlet or nozzle38' is provided for use during flight or non-noise suppressionoperation. Hollow vanes 22 have the plurality of small holes or nozzles26 in their trailing edge and the single large opening 24 in its forwardor leading edge. A plurality of pivotable flaps Elti are shown in Fig. 5to be pivotable about inner body 28 at pivots 192 and to be in abuttingor sealing relation one to the other and lying against the forward edgeof hollow vane 22' so as to block off holes 24 in the forward edge ofhollow edge 22' so that no exhaust gas passes into hollow vanes 22' whenthe vanes are in their retracted or non-silencing position. To permitair to flow into these vanes from the high pressure area in which hole24 is located would be to introduce inefficiency into the jet enginepropulsion system area.

it will be noted that vanes 22' are shown in Figs. 5 and 6 to be in aclustered position downstream of inner body 28' where they form first anexpanding and then a contracting conical continuation of inner body 23'.James are roughly triangular in longitudinal cross section of whichtrailing edge 81 forms the base of the triangle, and the forward edge ofthe vane contains the other two triangle legs 83 and 85 plus apex 37.

To cause hollow vanes 22 to move in unison from their retracted ortailcone position as is shown in Figs. 5 and 6 to their operable orsuppressing positions as shown in 5A and 6A, vanes 22 must be rotatedradially outward at the same time that they are moved rearwardly ordownstream. Figs. 5A and 6A show hollow vanes 22' in their operableposition such that the exhaust gas flow passes between tailpipe 20' andinner body 28', through opening or hole 24 in the forward edge of hollowvane 22', then through hollow vane 22 to be discharged rearwardlythrough the plurality of small holes or nozzles 26' which direct the jetexhaust downstream so as to etfect thrust propulsion. In thisembodiment, vanes 22 are shaped to nearly abut one another in theirextended positions thereby diminishing the problem of the spacingbetween them referred to previously. In this configuration a sealingflap 82 is made integral with vane 22 to perform a sealing functionbetween adjacent vanes 22' when in their extended positions therebypreventing the discharge of exhaust gas through the area betweenadjacent vanes. Because sealing flap 3?. is of small size, the dragproblem introduced by its use is negligible, therefore, it is virtuallyradially extending.

The actuating mechanism 93 to move the plurality of vanes 22 in unisonis shown in Figs. 5 and 5A. The actuating system consists of fixedhollow rod or cylinder which pivotally carries link or arm 86 which, inturn, pivotally attaches to the trailing edge of each hollow vane 22' at92. Fixed member 84 also carried fixed piston S8, which extendssubstantially radially therefrom to engage the inner surface of axiallymovable hydraulic or pneumatic cylinder 90 to form pressurizablecompartments 8 and 1M therewith. Vane 22 is pivotally attached to link86 by pivot 92 and is further pivotally attached to cylindrical sealingunit 94, which projects from or is part of movable cylinder 90, at pivot96. As a high pressure fluid source, such as the air from compressorsection 14, is introduced into chamber 98, cylinder tit? movesrearwardly or to the right and since it is integrally attached toscaling cylinder 94, it moves cylinder 9 5 with it. The rearward orright movement of cylinder 99 causes vanes 22 to move from theirretracted position as shown in Figs. 5 and 6 to their operable orextended positions as shown in Figs. 5A and 6A. This is accomplished bythe pivot, in unison, of vanes 22 about pivots 96 on sealing cylinder 94and about pivots 92 on connecting links 86, which is in turn pivotingabout fixed unit 84 at pivot point 100. When movable cylinder 90 reachesits far right or rear position, vanes 22 are in their extended positionand the plurality of flaps have rotated about their pivot points 102, bywhich they are pivotally attached to inner body 28' and come to restagainst sealing cylinder 94 or abut against any stop lug. With vanes 22'so extended, the exhaust gas flow passes through them and through thesmall holes or nozzles 26 to effect noise suppression as describedpreviously.

To cause vanes 22 to move in unison to their nonoperative or tailconeposition as shown in Figs. 5 and 6, a pressure source is introduced intochamber 104 of cylinder and is removed from chamber 98 of cylinder 90 tocause movable cylinder 90 to move to its upstream or far left position,carrying sealing cylinder 94 therewith. In unison, an inward and forwardmovement to vanes 22' is effected, due to this forward movement of pivotpoint 96 and the radially inward movement of pivot point W. asconnecting link or rod 86 pivots about pivot 100 on fixed member 84. Dueto this angularity of this motion, the plurality of flaps 80 moveradially outward along edge 85 of hollow vanes 22' until they are seatedto cover the plurality of holes 24 in the forward edge of vanes 22 andabut one another to perform a sealing function. By way of comparison, todemonstrate that a smaller exhaust outlet is presented radiuswise bycontinuously exhaust outlet 38, it will be noted that radial dimensionof continuous outlet 33 which is effective when the 'vanes are in theirretracted, inoperable position is indicated as Rr in Fig. 5 while theradial dimension through which exhaust gas flows to get into hollowvanes 22' when in their operable position is designated as R0" in Fig.5A. This difference in radial dimension is desirable since it is theintention of this noise suppression mechanism to be operable withoutadversely effecting engine thrust. To accomplish this, the thrustcreated by passing the exhaust gas through outlet 38' duringnon-silencing operation must be the same as that created by passing theexhaust gases through the plurality of small nozzles 26 during silencingor noise suppression operation.

The larger radial dimension of the exhaust outlet into hollow vanes 22',R, is necessary for the exhaust outlet presented by holes 24 is notcontinuous circumferentially as is outlet 38'.

' Further, when the noise suppression mechanism is in its retractedposition, the exhaust nozzle area at 33' is sized to engine requirementssuch that the exhaust gases are caused to increase to supersonicvelocity at the nozzle throat (smallest area). If exhaust gases wereintroduced into noise suppressor vanes 22 as supersonic velocity, therewould be damaging pressure and engine thrust losses. To prevent thrustloss, the gas passage area is increased in dimension, as from Rr to R0,thereby reducing gas velocity to reduce thrust losses by permitting thegas to more smoothly turn into vane 22. The exhaust gas velocity isincreased in velocity for thrust purposes as it passes through smallholes, apertures or nozzles 26' which direct the exhaust gasesdownstream during silencing operation.

Fig. 7 is shown to give a clearer demonstration of how the exhaust gaspasses through holes 24 at the forward edge of vanes 22, then throughvanes 22 to be discharged rearwardly through the plurality of holes ornozzles 26'.

Now referring to Figs. 8, 8A, 9, 9A and 11 we see another embodiment ofour invention in which both internal and external hollow vane noisesuppressors are used.

Figs. 9 and 9A show jet engine with convergent tailpipe and inner body28" and nacelle 110. Hollow vanes 22" are actuated and operated in thesame fashion as the vanes shown and described in Figs. 2 and 2A. Vanes22" are hollow vanes which may be rotated radially outward through theexhaust gas outlet 38 and extend radially beyond the tailpipe 20 andnacelle 110. Vanes 22 have a plurality of small holes, apertures ornozzles 26 in their trailing edge and of a single aperture or hole 24 intheir forward edge.

It will be recalled that in referring to the structure shown in Figs. 2and 2A it was necessary to provide inwardly directed troughs 42 to blockoff the area of the exhaust gas outlet between hollow vanes 22 when theywere in their extended or operable position. This was necessary so thatexhaust gas would be caused to pass through the plurality of small holesor nozzles 26, since these holes or nozzles would be the only exhaustarea available for the gas. The configuration shown in Figs. 8, 8A, 9,9A and 11 and Fig. 8A (see Fig. 8) utilizes the plurality of externalhollow vanes 112, which are pivoted about the outlet 79' of tailpipe 20at pivot 114 and are actuated-by any suitable unit such a pivotablehydraulic or pneumatic cylinder and piston unit 116 which is locatedexternally of tailpipe 20" and nacelle 110 and carries actuating rod 118which is pivotally attached to hollow vane 112 at pivot point 120. Ascompressed air or any other fluid source is provided to one or the otherside of piston 117, which is located within cylinder 116, the forcecreated will cause linkage 118 and hollow vane 112 to rotate or pivoteither in a forward or rearward direction. As shown in Figs. 8 and 11,vanes 112, are in their extended or noise suppressing position. As shownin Fig. 8A, vanes 112 are in their-retractedor forward position, whichis their inoperative position where they lie longitudinally againsttailpipe 20" or nacelle 110. Vanes 112 are positioned alternatelybetween vanes 22 and carry pie shaped segment 122 which abuts againstadjacent sides 124 and 12.6. of vanes 22" and have any opening oraperture 128 in a forward edge so that, when extended as shown in Figs.8'

and 11, the exhaust gas passes through the exhaust outlet formed bytailpipe 20" and inner body 28", through opening 128 in the forward edgeof vane 112, thence through vane 112 to be discharged rearwardly throughthe plurality of small holes or nozzles in the trailing edge of vane112. It will be noted in Fig. 8 that engine nacelle 110 projects beyondoutlet 79' of tailpipe 20" so as to form a convergent-divergent exhaustnozzle there with when the vanes are in their retracted or non-operativeFig. 5A, 6A position. It will be noted that surface 119 of nacelle 110is divergent radially outward from exhaust outlet 38".

By use of the embodiment shown in Figs. 8, 8A, 9, 9A and 11, all thearea of exhaust outlet 38" is not only blocked off to the normal gasflow so as to cause all exhaust gas to pass through the plurality ofsmall holes or nozzles 26" or 130, but also, the entire exhaust outlet38" is utilized effectively during noise suppression operation, andfurther, so that when vanes 112 and 22 are in their retracted ornon-silencing positions, a continuous and probably supersonic, exhaustoutlet 38" of convergent or convergent-divergent nozzle type ispresented for cruise or normal flight operation.

Now referring to Fig. 8A we see engine nacelle 110 which enclosestailpipe 20 and into which externally retractable vanes 112 are nestedin their retracted position. As a forwardly directed force is placedupon vanes 112 by connecting rods 118 due to the proper pressurizing ofvane actuating unit 116, so as to retract the vanes, it will be notedthat pie shaped segment 122 of vane 112 will snugly fit into pie shapedaperture 132 of nacelle 110 so as to perform an exhaust gas blockingaction and provide a smooth exhaust outlet for engine 10.

Pivotable doors 134 serve to enclose retracted vanes 122 when in theirretracted positions. Doors 134 are shown in cross section in Fig. 10 andconsist of two pivotable units 136 and 138 which have base members 140and 142 which are integrally attached to curved members 144 and 146 andeach pivots about points 148 and 150. In operation, when hollow vane 112is rotated so as to go into its inoperative or retracted position, theforward edge of vane 112 contracts and depresses base members 140 and142 to cause them to pivot about points 148 and 150 thereby closing thedoor unit 134 about the retracted vane 112 as shown on Fig. 10. Basemembers 140 and 142 are provided at the forward end of door unit 134only. When vane 112 is to be rotated into its operable position, aforward movement by linkage 118 is translated into a rotary motion invane 112 so as to release the pressure against base units 140 and 142and apply a similar pressure to units 144 and 146, to cause them to openandpermit the vane to go into its operable position. Here again, it willbe noted that we have caused the engine exhaust gas to pass through aplurality of small apertures so that predominately high frequency, noiseis created. Further, as described supra, the total flow characteristicsthrough exhaust outlet 38 is the same as through apertures 130 and 26.Due to the movement of inner body 28", a relatively small area exhaustoutlet 38" of convergent-divergent type is presented during normalflight when the exhaust gases may be at supersonic speed while a larger,lower velocity opening is provided during noise suppression operation todiminish aerodynamic losses in causing the exhaust gas to turn intovanes 22 and 112. It should be borne in mind that while not necessarilyso limited, the construction and actuation of vanes 22" of Fig. 9 isidentical to the construction and actuation of vanes 22 of Fig. 2.

It will be obvious to those skilled in the art that limits of vanemovement are defined by vane abutment in the clustered position and byvane abutment against tail pipe 20 in the operable position.

It should be noted that in any of our configurations, turning vanes maybe used at the inlet of the hollow vanes to assist exhaust gas turning.

We claimi 1. A device for suppressing the noise of a jet engine exhaustcomprising a tailpipe, an inner body substan tially concentric with andcontained within said tailpipe so as to form a gas passage therebetween,a plurality of hollow vanes each having a relatively large aperture inone side and a plurality of relatively small apertures in another side,said vanes being rotatably mounted on said device for movement from aclustered position downstream of said inner body, where they form aconical continuation of the inner body, outwardly to present said largeapertures to said gas passage with the plurality of relatively smallholes in the other side directed downstream, and means defining thelimits of movement of said vanes.

2. A device for suppressing the noise of a jet engine exhaust comprisinga tailpipe, an inner body substantially concentric with and containedwithin said tailpipe so as to form a gas passage therebetween, aplurality of hollow vanes mounted on said device and each having arelatively large aperture in one side and a plurality of relativelysmall apertures in another side, means to move said vanes from aclustered position downstream of said inner body, where they form aconical continuation of the inner body, outwardly to present said largeapertures to said gas passage with the plurality of relatively smallholes in the other side directed downstream, and means to block off saidgas passage between adjacent vanes when the vanes are moved outward.

3. A device for suppressing the noise of a jet engine exhaust comprisinga tailpipe, an inner body substantially concentric with and containedwithin said tailpipe so as to form a gas passage therebetween, aplurality of hollow vanes each having a relatively large aperture in oneside and a plurality of relatively small apertures in another side, saidvanes being mounted on said device for movement to a clustered positiondownstream of said inner body, where they form a conical continuation ofthe inner body, and to an outwardly extended position to present saidlarge aperture to said gas passage with the plurality of relativelysmall holes in the other side directed downstream, means to so move saidvanes, and means to substantially block oft" said gas passage betweenadjacent vanes when in the outwardly extended position.

4. A noise suppression mechanism comprising an outer duct and inner bodyconcentric with and located within said outer duct so as to form a gaspassage therebetween, a. plurality of elongated hollow vanes attached tosaid inner body and each having one hole in the forward edge thereof anda plurality of rearwardly directed small holes in the trailing edgethereof, an actuating mechanism connected to said vanes for moving themso that they may be clustered in conical form to provide a conicalextension of said inner body when in their inoperative position and sothat they may be extended radially outward beyond said outer duct whileextending across said gas passage so that said forward holes arepresented to said gas passage whereby said hollow vanes provide apassage between said small holes and said gas passage, and means toblock off said gas passage between said vanes when the vanes are intheir extended position.

5. A noise suppression mechanism comprising an outer duct and inner bodyconcentric with and located within said outer duct so as to form a gaspassage therebetween, a plurality of hollow vanes attached to said innerbody and each having one hole in the forward edge thereof and aplurality of rearwardly directed small holes in the trailing edgethereof, an actuating mechanism connected to said vanes for moving themto a clustered position to form a conical extension of said inner bodywhen in their inoperative position and to an operable position in whichthe vanes extend radially outward beyond said outer duct whiletraversing said gas passage so that said forward hole is presented tosaid gas passage and said hollow vane connects said small holes to saidgas passage while said small holes are directed downstream, and aplurality of inwardly directed troughs each projecting from said outerduct to said inner body so that said troughs blend smoothly into saidouter duct at their forward ends and project progressively inward untilthey are in close relation to said inner body at their downstream endsto block said gas passage between said vanes when said vanes are in saidoperable position.

6. In combination with an aircraft jet engine having a compressorsection, a combustion chamber section and a turbine section, a noisesuppression mechanism attached to the downstream end of said turbinesection comprising an outer duct of circular cross-section, and innerbody of circular cross-section concentric with and located within saidouter duct so as to form the engine exhaust gas passage therebetween, aplurality of hollow vanes attached to said inner body and each havingone hole in the forward edge thereof and a plurality of rearwardlydirected small holes in the trailing edge thereof, and an actuatingmechanism connected to said vanes for moving them so that they may beclustered in conical form just downstream of said inner body when intheir inoperative position to form the engine tailcone therewith and sothat said vanes may be extended radially outward beyond said outer ductwhile traversing said exhaust passage whereby said forward holes connectsaid exhaust gas passage through said hollow vanes to said small holesto cause the engine exhaust gas passing through said gas passage to passthrough said vanes and be discharged rearwardly through said smallholes.

7. A noise suppression mechanism comprising an outer duct of circularcross-section, and axially movable inner body of circular cross-sectionconcentric with and located within said outer duct so as to form a gaspassage therebetween, a plurality of hollow vanes attached to said innerbody and each having one hole in the forward edge thereof and aplurality of rearwardly directed small holes in the trailing edgethereof, an actuating mechanism connected to said vanes for moving themto a clustered position of conical form to provide a conical extensionof said inner body when said inner body is in its farthest rearwardposition and said vanes are in their inoperative position and for movingthem to an operable position in which the vanes extend radially outwardbeyond said outer duct while extending across said gas passage so thatsaid forward hole is presented to said gas passage when said inner bodyis in its farthest forward position so that said hollow vanes formpassages between said gas passage and said small holes which are nowrearwardly directed.

8. A device for suppressing the noise of a jet engine exhaust comprisinga convergent tailpipe of circular cross-section, a convergent andaxially movable inner body substantially concentric with and containedwithin said tailpipe so as to form a gas passage therebetween and forman exhaust outlet therewith, and a plurality progressively inwardlydirected troughs circumferentially spaced about said tailpipe and eachprojecting from said tailpipe to said inner body such that the forwardends of said troughs blend smoothly with said tailpipe while therearward ends of said troughs are in close relation to said inner bodyso as to cause said gas passage to be symmetrical but non-continuous, aplurality of elongated hollow vanes mounted on said device for movementand each having a relatively large aperture near the base of its leadingedge and having a plurality of relatively small apertures in itstrailing edge, vane actuating means attached to said vanes comprising apressurized cylinderpiston unit to move said vanes into a clusteredposition immediately downstream of said inner body when said inner bodyis in its farthest downstream position in which clustered position thevanes form a smooth conical continuation of the inner body to form anengine tailcone therewith, said tailcone being of such size to saidvanes outwardly to present said large leading edge apertures to said gaspassage while said vanes abut said tailpipe, said inner body andadjacent troughs while said inner body is in its farthest upstreamposition where said innerbody forms a larger gas passage with saidtailpipe due to its convergent shape and while the plurality ofrelatively small trailing edge holes are directed downstream, saidactuating means also actuating said inner body.

'9. A device for suppressing the noise of a jet engine exhaustcomprising a tailpipe having an outlet, an inner body substantiallyconcentric with and contained within said tailpipe and terminating shortof said tailpipe outlet so as to form a gas passage therebetween, aplurality of hollow vanes each having a relatively large aperture in oneside and a plurality of relatively small apertures in another side, saidvanes being movable from a clustered position'downstream of said innerbody, where they form first an expanding and then a contracting conicalcontinuation of said inner body so that a relatively small exhaustoutlet is formed between said tailpipe and said vanes so clustered,outwardly to an operable position in which said large apertures arepresented to an enlarged gas passage due to the movement and positioningof said vanes rearwardly while the plurality of relatively small holesin the other sides of said vanes are directed downstream, and means toblock ofi D said gas passage between adjacent vanes when said vanes arein said operable position.

10. A device for suppressing the noise of a jet engine exhaustcomprising a tailpipe having an outlet, an inner body substantiallyconcentric with and contained within said tailpipe and terminating shortof said tailpipe outlet so as to form a gas passage therebetween, aplurality of hollow vanes each having a relatively large aperture in afirst side and a plurality of relatively small apertures in a secondside, said vanes being mounted on said device for movement to aclustered position downstream of said inner body Where they form firstan expanding and then a contracting conical continuation of said innerbody due to the shape of said vanes so that a relatively small exhaustoutlet is formed between said tailpipe and said vanes so clustered, andfor movement from said clustered position outwardly to an operableposition to present said large aperture to an enlarged gas passage dueto the movement and positioning of said vanes rearwardly while theplurality of relatively small holes in the second sides are directeddownstream, and means to block off said gas passage between adjacentvanes when said vanes are in said operable position, and means to somove said vanes.

11. A device for suppressing the noise of a jet engine exhaustcomprising a tailpipe having an outlet, a-fixed inner body substantiallyconcentric with and contained within said tailpipe and terminating shortof said tailpipe outlet so as to form a gas passage therebetween, aplurality of hollow vanes each having a relatively large aperture in oneside and a plurality of relatively small apertures in another side, saidvanes being positionable in a clustered position downstream of saidinner body where they form first an expanding and then a contractingconical continuation of said inner body so that a relatively smallexhaust outlet is formed between said tailpipe and said vanes soclustered, means to seal said large vane apertures from said gas passagewhen said vanes are so'clustered, said vanes also being positionableoutward to present said large apertures to an enlarged gas passage dueto the movement of said vanes and sealing means while the plurality ofrelatively small holes are directed downstream, means to block off saidgas passage between adjacent vanes when said vanes are moved outward,and means to so position said vanes.

12. A device for suppressing the noise of a jet engine exhaustcomprising a tailpipe having an outlet, a fixed inner body substantiallyconcentric with and contained within-said tailpipe and terminating shortof said tailpipe outlet to form a gas passage therebetween, a pluralityof hollow vanes each having a relatively large aperture in one side anda plurality of relatively small apertures in another side, said vanesbeing movable to a-clustered position downstream of said inner bodywhere they form first an expanding and then a contracting conicalcontinuati n of said inner body whereby a relatively small continuousexhaust outlet is formed between said tailpipe and said vanes soclustered, means to seal said large apertures from said gas passage whensaid 'vanes are so clustered, said vanes also being movable in unisonand rearwardly and outwardly simultaneously to an operable position topresent said large aperture to an enlarged gas passage due to themovement and positioning of said vanes rearwardly and in which operableposition the plurality of relatively small holes in the other sides aredirected downstream, means to block off said gas passage betweenadjacent vanes when said vanes are in said operable position, and vaneactuating means comprising a pressurizable cylinder unit which isaxially movable and to which each of said vanes pivotally attach, afixed piston unit contained within and forming pressurizablecompartments with said movable cylinder, and an arm pivotally attachedto each of said vanes and beingpivotally attached to a fixed point insaid actuating means.

13. A device for suppressing the noise of a jet engine exhaustcomprising a tailpipe having an outlet, an inner body substantiallyconcentric with and contained within said tailpipe and terminating shortof said tailpipe outlet to form a gas passage therebetween, a pluralityof hollow vanes each having a relatively large aperture in its forwardedge and a plurality of relatively small apertures in its trailing edge,each of said vanes being roughly triangular in longitudinalcross-section with said trailing edge as the triangle base and whichforward edge includes the other triangle legs including the triangleapex, said vanes being retractable to a clustered position downstream ofsaid inner body where they form first an expanding and then acontracting conical continuation of said inner body due to the shape ofsaid vanes whereby a relatively small supersonic exhaust outlet isformed between said tailpipe out-let and said vane apexes, said vanesalso being movable rearw-ardly and outwardly to an operable position topresent said large aperture to an enlarged gas passage due to themovement and positioning of said vanes rearwardly while the plurality ofrelatively small holes in the other cdge directed downstream, means toblock off said gas passage between adjacent vanes when said vanes are insaid operable position, and means "to actuate said vanes.

14. A device for suppressing the noise of a jet engine exhaustcomprising a tailpipe, an inner body substantially concentric with andcontained within said tailpipe so as to form a gas passage therebetween,a first plurality of hollow vanes mounted on said device for movementand each having a relatively large aperture in one side and a pluralityof relatively small apertures in another side, said vanes being movablefrom a clustered position downstream of said inner body, where they forma conioal continuation of the inner body, outwardly to an operableposition to present said large apertures to said gas passage while theplurality of relatively small holes 'in the other edges are directeddownstream, 'and a second plurality of hollow vanes mounted on saiddevice for movement and each having a relatively large aperture in oneside and a plurality of relatively small apertures in another side, saidsecond plurality of vanes being movable from a retracted positionexternal of said tailpipe outwardly tocan operable position to presentsaid large aperture to said gas passage in locations between the vanesof said first plurality while the plurality of relatively small holesinsaid second vane plurality are directed downstream.

15. A device for suppressing the noise of a jet engine exhaustcomprising a tailpipe, an inner body substantially concentric with andcontained within said tailpipe so as to form a gas passage therebetween,a first plurality of hollow vanes mounted on said device for movementand each having a relatively large aperture in one side and a pluralityof relatively small apertures in another side, said vanes being movablefrom a clustered position downstream of said inner body, where they forma conical continuation of the inner body, outwardly to an operableposition to present said large apertures to said gas passage while theplurality of relatively small apertures are directed downstream, asecond plurality of hollow vanes mounted on said device for movement andeach having relatively large aperture in one side and a plurality ofrelatively small apertures in another side, said second plurality ofvanes being movable from a retracted position external of andlongitudinally against said tailpipe out- Wardly to an operable positionto present said large aperture to said gas passage in locations betweenthe vanes of said first plurality while the plurality of relativelysmall holes in said second vane plurality are directed downstream, meansto actuate said first plurality of vanes, and means to actuate saidsecond plurality of vanes.

16. A device for suppressing the noise of a jet engine exhaustcomprising a tailpipe, an axially movable inner body substantiallyconcentric with and contained within said tailpipe so as to form a gaspassage therebetween, a first plurality of elongated hollow vanes eachpivotally attached to said inner body and each having a relatively largeaperture in its leading edge and a plurality of relatively smallapertures in its trailing edge, said vanes being movable from aclustered position downstream of said inner body, where they form aconical mounted on said device for movement and located ex ternally ofsaid tailpipe and each having a relatively large aperture in one sideand plurality of relatively small apertures in another side, said secondplurality of vanes being movable between a retracted positionlongitudinally against said tailpipe outwardly to an operable positionto present said large aperture to said gas passage in locations betweenthe vanes of said first plurality while the plurality of relativelysmall holes in said second vane plurality are directed downstream, meansto actuate said first plurality of vanes, means to actuate said secondplurality of vanes, and means to actuate said inner body 17. A devicefor suppressing the noise of a jet engine exhaust comprising aconvergent tailpipe of circular crosssection, a convergent and axiallymovable inner body substantially concentric with and contained withinsaid tailpipe to form a gas passage therebetween and form an exhaustoutlet therewith, a plurality of elongated hollow vanes each having arelatively large aperture near the base of their leading edge and havinga plurality of relatively small apertures in their trailing edge, vaneactuating means attached to said vanes comprising a pressurizedcylinder-piston unit to move said vanes into a clustered positionimmediately downstream of said inner body when said inner body is at oneend of its travel Where the vanes form a smooth conical continuation ofthe inner body to form an engine tailcone therewith, said tailcone beingof such size to form an exhaust gas outlet of relatively small totalarea with said tailpipe, said actuating means also moving said vanesoutwardly to an extended position to present said large leading edgeapertures to a larger gas passage formed when said inner body is at theopposite end of its travel where said inner body forms a larger gaspassage with said tailpipe due to its convergent shape, and while theplurality of relatively small trailing edge holes are directeddownstream.

Brame Aug. 16, 1955 Johnson Nov. 27, 1956

